A. Field of the Invention
This invention relates to the field of solid state electronics, and particularly to the fabrication of solid state electronic devices from GaAs.
B. Description of the Prior Art
GaAs is a semiconducting compound which has a higher electron mobility than the semiconducting element silicon. This property plus the availability of high reistivity (semi-insulating) GaAs substrates offers the potential of providing integrated circuits having higher speeds and lower power requirements than the presently used silicon integrated circuits. However, the fabrication of devices from GaAs has proved to be a difficult problem, and it has not been possible to simply adopt the highly developed art of fabricating silicon integrated circuits to the fabrication of GaAs integrated circuits.
Previous GaAs integrated circuits have used the depletion-mode, GaAs MESFET mesa fabrication technology. Basic limitations of the mesa technique, such as the use of epitaxial layers or single implants, prevent the realization of high density, high yield, small geometry GaAs devices and integrated circuits.
Ion implantation has been utilized as a technique for implanting dopants into a GaAs substrate, see for example U.S. Pat. No. 3,914,784, entitled, "Ion Implanted Gallium Arsenide Semiconductor Devices Fabricated in Semi-Insulating Gallium Arsenide Substrates" to Hunsperger, et al. However, reproducibility of the implanted profiles is poor, particularly for low dose implants. Consequently, ion implantation has not been satisfactory for reliably fabricating integrated circuits in GaAs.